linux-kernel - Re: [RFC PATCH 1/3] mm, reclaim: make should_continue

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Date:   Fri, 26 Jul 2019 09:12:25 +0100
From:   Mel Gorman <mgorman@...e.de>
To:     Hillf Danton <hdanton@...a.com>
Cc:     Mike Kravetz <mike.kravetz@...cle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Michal Hocko <mhocko@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Johannes Weiner <hannes@...xchg.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC PATCH 1/3] mm, reclaim: make should_continue_reclaim
 perform dryrun detection

> From: Hillf Danton <hdanton@...a.com>
> Subject: [RFC PATCH 1/3] mm, reclaim: make should_continue_reclaim perform dryrun detection
> 
> Address the issue of should_continue_reclaim continuing true too often
> for __GFP_RETRY_MAYFAIL attempts when !nr_reclaimed and nr_scanned.
> This could happen during hugetlb page allocation causing stalls for
> minutes or hours.
> 
> We can stop reclaiming pages if compaction reports it can make a progress.
> A code reshuffle is needed to do that. And it has side-effects, however,
> with allocation latencies in other cases but that would come at the cost
> of potential premature reclaim which has consequences of itself.
> 
> We can also bail out of reclaiming pages if we know that there are not
> enough inactive lru pages left to satisfy the costly allocation.
> 
> We can give up reclaiming pages too if we see dryrun occur, with the
> certainty of plenty of inactive pages. IOW with dryrun detected, we are
> sure we have reclaimed as many pages as we could.
> 
> Cc: Mike Kravetz <mike.kravetz@...cle.com>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Michal Hocko <mhocko@...nel.org>
> Cc: Vlastimil Babka <vbabka@...e.cz>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Signed-off-by: Hillf Danton <hdanton@...a.com>

Acked-by: Mel Gorman <mgorman@...e.de>

Thanks Hillf

-- 
Mel Gorman
SUSE Labs